1. Field of the Invention
The present invention concerns a projection type display apparatus that comprises light source units comprising cooling means and light emitting units that include light emitting layers comprising organic EL (electroluminescence) elements, wherein the light emitted from the light emitting units is guided to liquid crystal panels, and the images displayed on the liquid crystal panels are enlarged and projected by a lens or lenses.
The present invention also concerns cooling control technology for cooling the light emitting units that employ light emitting layers made up of organic EL (electroluminescence) elements and that are used in various fields. More particularly, the present invention pertains to a light source apparatus formed by adding temperature detection means or elapsed time measuring means to light source units comprising light emitting units and cooling means, and to a method and apparatus for controlling a light source apparatus that controls the cooling means by the temperature detection means or elapsed time measuring means in the light source apparatus.
2. Description of the Related Art
In recent years, with the amazing advances being made in semiconductor technology, various electronic display devices other than CRT displays are being developed and turned into marketable products. One of these which is drawing much attention is the projection display apparatus, a technology that is advantageous in terms of lower power consumption and lighter weight.
One type of such a projection display apparatus that is known is the liquid crystal projector wherewith images on a liquid crystal panel are enlarged and projected by a projection lens onto a reflective or transmissive screen and thus displayed. One example of such a liquid crystal projector is diagrammed in FIG. 31.
The liquid crystal projector diagrammed in FIG. 31 comprises a light source lamp unit 202 inside a cabinet. Electrical discharge lamps such as metal halide lamps, or halogen lamps, are used in the light source lamp unit 202. The light emitted from this light source lamp unit 202 is guided via a mirror 203 to dichroic mirrors 204 and 205, whereby it is separated into red light, green light, and blue light. Of the three color components into which the light is separated, the red light passes by way of a mirror 206 to a red displaying liquid crystal panel 209, the green light is led directly to a green displaying liquid crystal panel 210, and the blue light is led by way of mirrors 207 and 208 to a blue displaying liquid crystal panel 211.
The images displayed on the three liquid crystal panels 209 through 211, respectively, are illuminated by their respective colors, and this light is combined by a dichroic prism 212. The combined light is enlarged by a projection lens 213 and projected, in enlarged form, on a reflecting screen (not shown), for example.
With a liquid crystal projector in which a light source lamp unit 202 such as this is used, however, the light emitted from the metal halide lamp or halogen lamp must be radiated with good parallelism onto the liquid crystal panel. For this purpose, as diagrammed in FIG. 31, it is necessary to provide the light source lamp unit 202 with a reflector 202A having a rather large aperture. This constitutes a serious problem in that it makes it difficult to meet the demand for lighter weights and smaller sizes in the overall projector.
As is depicted in FIG. 31, moreover, it is preferable that the lamp in the light source be cooled. The larger the capacity of the lamp, in fact, the higher must the cooling capability of the cooling fan be.
In the case of a so-called triple liquid crystal projector, moreover, in which three separate liquid crystal panels are provided for the red, green, and blue colors, as described in the foregoing, a light dividing optical system is necessary to take the light emitted from the single-lamp light source and divide it into the colors on the three liquid crystal panels. This makes it even more difficult to achieve the desired reduction in weight and size.
A first example of the related art is now discussed. In recent years, in an effort to break out of this dilemma, the use of organic EL elements as the light emitting unit has been proposed. This reflects the fact that many reports have been made of light of high brightness being emitted by EL elements using an organic thin film for the light emitting layer. These light emitting units are thin planar light sources in which are formed an electric-field light-emission (electroluminescence=EL) layer consisting of an organic thin film. Compared to inorganic EL elements, organic EL elements can operate at low voltage and provide high brightness. Thus they are believed to be well suited for use in enlarging-projection type projection display apparatuses, and much research is being focused on the practical implementation of such devices.
An example of a triple liquid crystal projector in which such organic EL elements are used as the light source unit is diagrammed in FIGS. 32 and 33. In the liquid crystal projector depicted in these drawings, light source units 224, 225, and 226, in which are used organic EL elements that emit red, green, and blue light, respectively, are positioned, respectively, behind and in close proximity to three liquid crystal panels 221, 222, and 223, which display red, green, and blue colors. Item 227 is a dichroic prism, and 228 is a projection lens. An example of this type of projection display apparatus is disclosed in laid-open patent application (Tokkai) S51-119243 [1976] (gazette).
Even with such a triple liquid crystal projector such as this however, in which organic EL elements are used as the light source unit, the organic EL elements produce heat when they are driven, and thus require cooling.
A second example of the related art is now discussed. One possible means of forcibly cooling such organic EL elements as these is to employ electrical cooling elements that utilize the peltier effect.
Nevertheless, in the liquid crystal projector of the first example of the related art depicted in FIGS. 32 and 33 and described above, a planar light emitting unit in which organic EL elements are used is employed, thus making it possible to achieve smaller sizes and lighter weights, but some unresolved problems remain, as noted below. These problems present obstacles which prevent this technology from being practically implemented.
In the first place, even though these are called organic EL elements, they produce heat when they are driven, and this emission of heat causes the light emitting performance to gradually deteriorate, shortening the useful life of the elements.
Furthermore, if the light emission performance of a light source unit in which organic EL elements are used has fallen below allowable limits, then one would like to be able to replace only the light source unit. In a color-displaying triple liquid crystal projector, in particular, light source units are provided for each of the three liquid crystal panels, no the number thereof in high. A deterioration in the performance of one or two of the light source units destroys the color balance of the displays on the screen, so the effects thereof are great. In such cases, it would be economical to be able to simply replace only those light source units which have reached the limit of their useful life. Previously, however, no structure has been proposed for such light source units which would make them independent and easily replaceable. This has obliged repair personnel to go to the great trouble of changing out light source units on boards on which they are mounted.
When making such replacements, it is very important not only to insure the electrical connection with the light source unit after replacement, but also to insure that it has been restored to the prescribed optical position. If the orientation or position of the replaced light source unit is off, the way in which light strikes the liquid crystal panels will be altered, the picture on the screen may be partially darkened, and the display performance may be degraded.
Another important aspect to consider when making replacements is rightly judging when exactly to make the replacement. If such replacement is made late, brightness may be reduced, and viewers may have to put up with pictures that exhibit distorted color balance. Conversely, if the replacement is made too early, that will adversely affect economy. In other words, it is important to judge when the right time to make the replacement is. Previously, however, no effective way to remedy this had been proposed.
Furthermore, the light emitted from planar light source units in which organic EL elements are used is not necessarily parallel, and when it strikes a liquid crystal panel it exhibits the property of widely spreading out. For this reason, the light emitted from the light source units contains much wasted light that does not contribute to the display of the image on the liquid crystal panels, by which measure the brightness of the displayed picture deteriorates. Moreover, efforts to raise the display brightness to compensate for this wasted light result in recklessly raising the light emission output of the organic EL elements, which leads to a vicious cycle in which the heat generated degrades the light emission performance and leads to even more severe shortening of useful life.
In terms of enhancing the efficiency with which light is emitted from this light source unit, transparent glass plates placed on the emission side of the organic thin films making up the organic EL elements play an important role. Conventionally, however, these plates have been of a simple form in which both front and back surfaces are parallel. With the first example of the related art discussed above, it has been very difficult to achieve a practical projection display apparatus due to the many problems cited.
With the second example of the related art, moreover, when light emitting units comprising organic EL elements, and cooling means, are employed, and electronic cooling elements are used to cool the organic EL elements, if one begins driving the cooling elements simultaneously with lighting the organic EL elements, the temperature of the organic EL elements will rise before they are cooled, whereupon the organic EL elements will be thermally degraded, which constitutes a problem.
When the cooling elements are activated first, and the organic EL elements are lighted subsequently, the organic EL elements are cooled before they emit light, causing dew to form. This also constitutes a problem.
Furthermore, when the use of the light source apparatus is discontinued, if the timing between extinguishing the organic EL elements and stopping the cooling elements is improper, either the organic EL elements will suffer thermal degradation or dew will be formed. This constitutes yet another problem. A first major object of the present invention is to provide a projection display apparatus in which are employed light source units comprising cooling means and a light emitting unit comprising organic EL elements, which is light in weight, is small in size, and can be practically implemented.
One specific object of the present invention is to make it possible to prevent degradation in light emission performance caused by heat generation in the organic EL elements, thereby making it possible to increase useful life, stabilize brightness, and secure maximum brightness continually.
Another specific object of the present invention it to establish independent light emitting units comprising organic EL elements, such that they can easily be replaced so that their electrical connection and optical positioning are secured, and so that the replacement operation is rendered more efficient and maintenance and inspection are made easier.
Another specific object of the present invention is to make it possible to easily judge when replacements should be made, thus making it possible to insure high picture display quality, and rendering maintenance and inspection easier.
Another specific object of the present invention is to enhance the efficiency with which light strikes the liquid crystal panels.
Another specific object of the present invention is to enhance the efficiency with which light is emitted from the light source unit by the organic EL elements, by improving the transparent substrates on which the light source units are mounted.
A second major object of the present invention in to provide a light source apparatus wherewith it is possible to prevent both thermal degradation in the organic EL elements and the formation of dew, together with a method and an apparatus for controlling the light source apparatus.
In order to achieve the first object cited above, the projection display apparatus according to the present invention comprises: transmissive liquid crystal panels that display images; light source units that are positioned on the back side of the liquid crystal panels and that comprise light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units; and a projection lens positioned in front of the liquid crystal panels for enlarging images displayed on the liquid crystal panels and projecting them onto a screen. For example, the cooling means exhibit a structure wherein there are electronic cooling means utilizing the Peltier effect positioned at the back of reflecting electrode layers positioned at the back of the light emitting units, and thermal conductors that conduct generated heat are interposed between the reflecting electrode layers and the light emitting layers.
For example, moreover, the cooling means comprise cooling bodies provided with heat-radiating fins that conduct and radiate the generated heat, provided at the back of reflective electrode layers positioned at the back of the light emitting layers, and sealing substrates that seal off the portions of light emitting film structures that include the reflecting electrode layers, and that integrate the sealing substrates and the cooling bodies.
Also, the surface areas of the heat-radiating fins of the cooling bodies are formed so that the center portions of the light emitting units are larger than the end portions.
For example, moreover, the organic EL elements are elements that generate white light.
For example, moreover, the liquid crystal panels comprise three liquid crystal panels that separately display images in red components, green components, and blue components, the organic EL elements comprising three organic EL elements that separately generate red, green, and blue light, exhibiting a structure wherein a dichroic prism is interposed in the optical path between the three liquid crystal panels and the projection lens.
In order to achieve the first object and the specific objects noted above, the projection display apparatus to which the present invention pertains comprises: transmissive liquid crystal panels that display images; light emitting units positioned in back of the liquid crystal panels and provided with light emitting layers comprising organic EL elements; and attachment means for attaching the light emitting units, such that they can be freely attached and detached, to at least the portion of a base on which is mounted the liquid crystal panels and the light emitting units.
For example, moreover, the light emitting units comprise bases that mount both electrode layers that sandwich the light emitting layers and terminals that are electrically connected to the electrode layers, while the attachment means are equipped both with connectors that plug terminal units into the base portions, such that they can be freely plugged and unplugged, the terminal units having mounted in them the terminals of the boards, and with guides that guide the boards in the direction of connector plug-in, when the terminal units of the boards are inserted into the connectors.
For example, moreover, light source units are provided which comprise cooling means for radiating heat generated by the light emitting layers, and light emitting units containing the light emitting layers.
For example, moreover, the cooling means comprise heat-radiating fins that are provided on the back side of the reflective electrode layers positioned at the back of the light emitting layers, which conduct and radiate the generated heat.
Furthermore, in order to achieve the first object noted above, the projection display apparatus to which the present invention pertains comprises transmissive liquid crystal panels that display images, and light emitting units, positioned at the back of the liquid crystal panels, in which light emitting layer structures having light emitting layers made up of organic EL elements are provided on transparent substrates, wherein means for raising the light-emission efficiency are formed integrally on the light emitting surfaces of the transparent substrates of the light emitting units.
For example, moreover, the means for raising the light-emission efficiency are microlens arrays formed two-dimensionally on the light-emission surfaces.
For example, moreover, the means for raising the light-emission efficiency are microprism arrays formed two-dimensionally on the light-emission surfaces.
In order to achieve the first object and the specific objects noted earlier, the projection display apparatus to which the present invention pertains comprises light emitting units positioned at the back of liquid crystal panels and having light emitting film structures, the light emitting layers of which are organic EL elements, provided on transparent substrates; voltage measuring means for measuring voltages on terminals between the electrodes of the light emitting film structures; useful-life assessment means that assess the useful life remaining in the light emitting film structures; and announcement means that announce the useful life when the useful-life assessment means have assessed the useful life. Here, for example, the useful-life assessment means are means that assess the useful life by converting the values of the voltages on the terminals to brightness values and comparing these against reference values.
For example, moreover, here are comprised color-balance assessment means for assessing the red, green, and blue color balance on the basis of the terminal voltage values measured by the voltage measuring means, and color-balance correction means that automatically correct the color balance on the basis of the results of the assessments of the color-balance assessment means.
For example, moreover, the light emitting layer structure for the light emitting units comprises a resonator structure that selectively resonates and emits light of a particular wavelength.
In order to achieve the two objects noted above, the light source apparatus to which the present invention pertains comprises light source units comprising light emitting units provided with organic EL elements an light emitting layers and cooling means provided In the-light emitting units for radiating heat generated by the light emitting units; and temperature detection means for measuring the temperature of the cooling means.
In order to achieve the two objects noted above, the light source apparatus to which the present invention pertains comprises light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units; and temperature detection means for measuring the temperature of the organic EL elements.
In order to achieve the two objects noted above, the light source apparatus to which the present invention pertains comprises light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units; and at least one or other of elapsed time measuring means for measuring the elapsed time after the start of the cooling means or elapsed time measuring means for measuring the elapsed time after the stopping of the cooling means.
In order to achieve the two objects noted above, the light source apparatus control method to which the present invention pertains is a light source apparatus control method for controlling cooling starts and the lighting of a light source comprising light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and temperature detection means for measuring the temperature of the cooling means; wherein the organic EL elements are lighted at the point in time when the temperature detected by the temperature detection means reaches a set temperature, after the cooling means have been started.
In order to achieve the two objects noted above, the light source apparatus control method to which the present invention pertains is a light source apparatus control method for controlling cooling starts and the lighting of a light source comprising light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and temperature detection means for measuring the temperature of the organic EL elements; wherein the organic EL elements are lighted at the point in time when the temperature detected by the temperature detection means reaches a set temperature, after the cooling means have been started.
In order to achieve the two objects noted above, the light source apparatus control method to which the present invention pertains is a light source apparatus control method for controlling cooling stoppages and the extinguishing of a light source comprising light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and temperature detection means for measuring the temperature of the cooling means; wherein after reducing the drive current going to the organic EL elements, the cooling means are stopped, and the organic EL elements are extinguished at the point in time when the temperature detected by the temperature detection means reaches a set temperature.
In order to achieve the two objects noted above, the light source apparatus control method to which the present invention pertains is a light source apparatus control method for controlling cooling stoppages and the extinguishing of a light source comprising light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and temperature detection means for measuring the temperature of the organic EL elements; wherein after reducing the drive current going to the organic EL elements, the cooling means are stopped, and the organic EL elements are extinguished at the point in time when the temperature detected by the temperature detection means reaches a set temperature.
In order to achieve the two objects noted above, the light source apparatus control method to which the present invention pertains is a light source apparatus control method for controlling cooling starts and the lighting of a light source comprising light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and elapsed time measuring means for measuring the elapsed time from the start of the cooling means; wherein the organic EL elements are lighted after a certain time has elapsed since the cooling means were started.
In order to achieve the two objects noted above, the light source apparatus control method to which the present invention pertains is a light source apparatus control method for controlling cooling stoppages and the extinguishing of a light source comprising light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and elapsed time measuring means for measuring the elapsed time from the stoppage of the cooling means; wherein after reducing the drive current going to the organic EL elements, the cooling means are stopped, and the organic EL elements are extinguished a certain time thereafter.
In order to achieve the two objects noted above, the light source apparatus control apparatus to which the present invention pertains is a control apparatus for a light source apparatus that comprises light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and temperature detection means for measuring the temperature of the cooling means, and that illuminates liquid crystal display elements with light radiated from the organic EL elements; wherein the light source apparatus is controlled so that, when lighting the organic EL elements, the organic EL elements are lighted at the point in time when, after the cooling means have been started, the temperature detected by the temperature detection means reaches a set value for lighting, and, when extinguishing the organic EL elements, the cooling means are stopped after reducing the drive current going to the organic EL elements, and the organic EL elements are extinguished at the point in time when the temperature detected by the temperature detection means reaches a set value for extinguishing.
In order to achieve the two objects noted above, the light source apparatus control apparatus to which the present invention pertains is a control apparatus for a light source apparatus that comprises light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and temperature detection means for measuring the temperature of the organic EL elements, and that illuminates liquid crystal display elements with light radiated from the organic EL elements; wherein the light source apparatus is controlled so that, when lighting the organic EL elements, the organic EL elements are lighted at the point in time when, after the cooling means have been started, the temperature detected by the temperature detection means reaches a set value for lighting, and, when extinguishing the organic EL elements, the cooling means are stopped after reducing the drive current going to the organic EL elements, and the organic EL elements are extinguished at the point in time when the temperature detected by the temperature detection means reaches a set value for extinguishing.
In order to achieve the two objects noted above, the light source apparatus control apparatus to which the present invention pertains is a control apparatus for a light source apparatus that comprises light source units comprising light emitting units provided with organic EL elements as light emitting layers and cooling means provided in the light emitting units for radiating heat generated by the light emitting units, and both elapsed time measuring means for measuring the elapsed time from the start of the cooling means and elapsed time measuring means for measuring the elapsed time from the stoppage of the cooling means, and that illuminates liquid crystal display elements with light radiated from the organic EL elements; wherein the light source apparatus is controlled so that, when lighting the organic EL elements, the organic EL elements are lighted after a certain time has elapsed since the cooling means were started, and so that, when extinguishing the organic EL elements, the cooling means are stopped after reducing the drive current going to the organic EL elements, and the organic EL elements are extinguished a certain time thereafter.
For example, moreover, the control apparatus for the light source apparatus is applied to a projection type projection display apparatus which takes images displayed on the liquid crystal display elements and enlarges and projects them by a projection lens.